PROJECT SUMMARY Reducing use of low-value care ? care for which potential for harm exceeds the possible benefit ? is an attractive but elusive goal in health care. It is one of the few opportunities to increase quality while decreasing spending on care, but there was traditionally little consensus on what constitutes low-value care and little opportunity to measure it and design interventions to target it. That has changed in recent years as a result of physician-led efforts in the United States and other countries to build consensus around what tests and procedures qualify as low-value, and a number of preliminary analyses aimed at quantifying use of low-value care, particularly among Medicare beneficiaries. Many services identified as low-value are routine imaging and laboratory tests. These services can be relatively low-cost and low-risk but they may initiate a cascade of subsequent services, or an entire patient episode of low-value care, with much greater impact on both patient outcomes and health care spending. Little is know about (i) the prevalence and variation in episodes of low- value care, including the cost of subsequent related services stemming from the index test; (ii) the effect of payment reform interventions on use of low-value care and related episodes; and (iii) which characteristics best position a provider organization to reduce use of low-value care. Addressing these knowledge gaps and reducing low-value care will both decrease harm to patients and reduce unnecessary spending. Aim 1 of this study is to construct episodes of low-value testing that include tests, procedures, and treatments related to an initial low-value test, and examine the prevalence and cost per episode. This analysis will build upon previously developed claims-based measures of overuse, and rely on use of 100% fee-for-service Medicare data. Aim 2 will focus on the effect of accountable care organization (ACO) implementation on utilization of episodes of low-value care. The Affordable Care Act authorized the Centers for Medicare and Medicaid Services to contract with ACOs, networks of providers responsible for the health care of a defined population. ACO providers are rewarded financially if they can slow growth in their patients? health care spending while maintaining or improving the quality of care they deliver. Aim 2 will involve assigning Medicare beneficiaries to ACOs using claims data and examining utilization and costs of episodes of low-value care pre- and post-ACO implementation in Medicare ACOs as compared with local control groups. Data from four waves of The National Survey of ACOs will then be linked with Medicare claims to understand, in Aim 3, which ACO characteristics are most closely associated with successful reduction in utilization of low-value care. We will also interview ten high-performing ACOs to identify tactics, facilitators, and challenges to reducing low- value services. This study will provide tools for future measurement of episodes of low-value care and inform the evolution of ACO policy as it pertains to the model?s capacity to reduce utilization of low-value care.